WHAT IS MERCURY?
Mercury is the most toxic of all natural metals and the only one that is liquid at room temperature. Named for the solar system’s fastest moving planet, and the winged sandaled messenger in Roman mythology because of its highly mobile elemental form, mercury readily cycles through the environment once released.
TOXIC EFFECTS OF MERCURY CONTAMINATION
Mercury’s toxic effects vary depending on the chemical form it takes and the way a person or animal gets exposed to it. The most dangerous form is methylmercury, also called organic mercury. While mercury is not present in the drinking water supply, it’s of great concern to the Santa Clara Valley Water District. Methylmercury tends to increase up the food chain, particularly in lakes.
- The mud at the bottom of a lake may have 100 or 1,000 times the amount of mercury than is in the water.
- Worms and insects in the mud extract and concentrate the organic mercury.
- Small fish that eat these critters further concentrate the mercury in their bodies.
- The chain continues as larger fish eat smaller fish until the top predator fish may have mercury levels up to 1,000,000 times the mercury level in the water.
Eating contaminated fish and other organisms at the top of the aquatic food chain is the most common way that people become exposed to methylmercury. It can cause problems with the immune system and damage a person’s nervous system, creating issues with coordination and the senses of touch, taste and sight. Because it’s readily absorbed when ingested and excreted very slowly, most of it stays in a person’s system. Pregnant women and young children are the most susceptible to mercury poisoning.
MERCURY IN THE ECOSYTEM
Mercury in aquatic environments takes on a vicious life of its own. Bacteria converts the metal into the more toxic methylmercury, which can be taken up by insects, the fish that eat the invertebrates and humans who eat the fish. Mercury’s concentration increases at each level up the food chain in a process known as biological magnification.
Exposure to mercury can be particularly hazardous for pregnant women and small children. During the first several years of life, a child’s brain is developing and rapidly absorbing nutrients. In adults, mercury poisoning can adversely affect fertility and blood pressure regulation and can cause memory loss, tremors, vision loss and numbness of the fingers and toes. A growing body of evidence suggests that exposure to mercury may also lead to heart disease.